Actuator for actuating a safety switch

ABSTRACT

An actuator is disclosed for actuating a safety switch. In at least one embodiment, the actuator includes a fixing element, an actuating element, and a connection arrangement for connecting the elements. A technical method is disclosed which proposes a universally applicable and low-cost activator. To this end, in at least one embodiment, the connection arrangement is implemented with at least one elastic element, which is pretensioned by way of at least one pretensioning element. Due in particular to the internal mounting of the pretensioning element inside the elastic element, a very simple and robust structure of the connection arrangement is achieved.

PRIORITY STATEMENT

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/DE2006/001137 which has anInternational filing date of Jun. 30, 2006, which designated the UnitedStates of America, the entire contents of which are hereby incorporatedherein by reference.

FIELD

At least one embodiment of the invention generally relates to anactuator for actuating a safety switch. In at least one embodiment, theactuator includes a fixing element, an actuating element and aconnection arrangement provided for connecting the fixing element to theactuating element. At least one embodiment of the invention alsogenerally relates to a safety switch having an actuator of the aforesaidkind.

BACKGROUND

Safety switches are generally used to force the activation ordeactivation of an electrical power supply. The fields of application ofsafety switches are legion. In the industrial as well as in the privatedomain, application scenarios such as, for example, a guard door, aprotective cover, a safety fence or similar arrangements can beimplemented with the aid of a safety switch.

In the present prior art safety switches of this kind have a basicstructure, hereinafter also referred to as a housing, and a separateactuator. The reason for this two-part implementation is to be found inthe way in which the safety switch is used. The separate actuator andthe housing are mounted on separate mechanical units in order to bebrought together for a specific operating state. Thus, for example, theseparate actuator could be mounted on a movable door, whereas thehousing of the safety switch could be fixed to a wall or a door frame.

The basic structure of the safety switch has a drive head and can be ofsingle- or multipart design. Furthermore the switching contacts arearranged in the basic structure. The drive head has one or more openingsinto which the actuator is introduced in order, for example, to closeopener contacts.

In the safe system state, which is given when the danger zone isscreened off by way of a protective device, the actuator is locatedinside the drive head. If, for example, a guard door on which theactuator is disposed is opened, the actuator is extracted from the drivehead, causing the system to be switched off, or placed in a safe state,as a result of the forced opening of the opener contact. If the systemcannot easily be switched off or, as the case may be, the dangerassociated therewith cannot easily be eliminated, the safety switch canalso be provided for the purpose of locking the guard door.

The precise insertion of the actuator proves problematic in the case ofthe mechanical actuation of the drive head by way of the actuator.Reliable introduction of the actuator into the drive head must thereforebe ensured under mechanical load and the actuating function reliablytriggered in spite of any deviations from the provided insertion path.This tolerance problem arises due to the fact that the drive head andthe separate actuator are mounted on different carriers which allow acertain amount of play. This problem is generally exacerbated withexposure of the safety switch to wear and tear, as a result of improperhandling of the protective device or due to deficient assembly right atthe time of commissioning. It can be assumed that in the standard casethe separate actuator has an unavoidable offset with respect to theinsertion opening of the drive head. With the actuator inserted,therefore, the actuator must be able to be aligned in accordance withthe insertion opening of the drive head.

Introduction of the actuator at an angle in the case of cover-likeprotection objects constitutes a further problem. This problem is basedon the fact that protective covers, for example, are not actuated in alinear manner, as are sliding doors for example. The movement of aprotective cover corresponds to a partial rotational movement about arotational axis which is mostly determined by way of hinges.Consequently it must be possible for the actuator to be inserted intothe drive head at a certain angle that requires to be set beforehand. Inthis way it is ensured that upon reaching an end position in the drivehead the actuator is aligned with respect to the same in anoperationally correct manner.

Flexible mounting of an actuator by way of rubber bushings likewiseproves problematic. For example, actuators are often secured to amounting surface by way of two screws, with the actuator plate beingflexibly mounted by way of rubber bushings and consequently only beingable to compensate to a very limited extent for tolerances between, forexample, a guard door and a frame. Because the drilled holes in theactuator plate are typically very much larger than the screw heads ofthe fixing screws, actuators of this kind must generally be mounted byway of large-sized retaining washers. If the ratio of retaining washerto drilled hole in the actuator plate does not correspond (the retainingwasher could be too small, for example), the rubber bushings can bemoved over the screw head, thereby creating a safety risk. A furtherdisadvantage with actuators of this kind is that a desired preferreddirection can only be pretensioned with considerable overhead.

DE 295 16 230 U1 discloses a radius actuator which is mounted on anelaborate base member. Because of its base member the actuator'spossible tolerance compensation is very limited. A lateral offset is notpossible and in addition the base member has a large number ofcomponents.

SUMMARY

At least one embodiment of the invention is directed to a simple anduniversally usable actuator which allows tolerance compensation in anydirections.

At least one embodiment of the invention includes an actuator whereinthe connection arrangement has at least one resilient element which ispretensioned by way of at least one pretensioning element for thepurpose of connecting the fixing element to the actuating element. Asafety switch is further disclosed.

At least one embodiment of the inventive actuator for actuating a safetyswitch has a fixing element, an actuating element and a connectionarrangement for connecting the fixing element to the actuating element.The connection arrangement also has at least one resilient element whichis pretensioned by way of at least one pretensioning element for thepurpose of connecting the fixing element to the actuating element. Inthis arrangement the function of the pretensioning element is to beresponsible for pretensioning the resilient element between the fixingelement and the actuating element. The pretensioning element andoptionally also the resilient element are provided in order to allowalignment in the actuating direction, whereby the resilient elementensures a flexible offset or deflection of the connection arrangement onall sides. The rigidity of the connection arrangement that is necessaryfor actuation purposes can be realized by the pretensioning element, bythe resilient element or by both elements together.

In an advantageous embodiment the actuating element is mounted on thefixing element in a spring-loaded manner by way of the resilientelement. In this arrangement the forced opening prescribed for thesafety switch is ensured by way of the rigidity of the pretensioningelement. In this case there is a clear division of the tasks of the twoelements which is advantageous when it comes to selecting thecomponents.

In an advantageous embodiment it is possible to pretension the resilientelement for tension or compression by way of the pretensioning element.As a result the actuator is always in a defined position. Through thecombination of these two elements the actuator can advantageously bedeflected laterally, compressed, twisted, offset in parallel and/orbent. An actuator constructed in this way can move at will in all axesand thus offers a maximum of tolerance compensation.

Advantageously, the pretensioning element is permanently connected tothe actuating element and the fixing element, thereby enabling stressessuch as impacts, shocks or similar to be absorbed by way of a, forexample, single-piece embodiment and avoiding a breaking-off of theactuator. If the resilient element should nonetheless break due, forexample, to heavy wear and tear or severe stress, the actuating elementis still connected to the fixing element by way of the pretensioningelement, with the result that misuse or a malfunction can be ruled out.

In an advantageous embodiment the pretensioning element is disposedinside the resilient element. As a result of this arrangement it isensured that the force reaction is similarly great for anticipateddirections of force application. The actuator reacts with the samecounterforce for different directions of force application. Furthermorethe structure of the connection arrangement is kept very simple,resulting in a cost saving owing to the small number of components.

The resilient element and the pretensioning element are advantageouslyembodied as a single piece, with the resilient properties of thesingle-piece embodiment varying radially, which is to say substantiallyperpendicularly with respect to the actuating direction. Thus, forexample, it is conceivable for the material density of the connectionarrangement to decrease continuously or in stages from the inside to theoutside.

Advantageously, the actuator has a mechanism for presetting theactuating direction of the actuating element. In this way it ispossible, for example, to provide a presetting mechanism betweenconnection arrangement and actuating element, or between connectionarrangement and fixing element, which presetting mechanism can be set asappropriate according to the application. This enables the actuator tobe employed universally for any conceivable application, effectively asa radius actuator or universal actuator. Optionally it is possible toprovide already preset angles for a quite specific application ex worksso that the user is no longer able to modify this angle.

In an advantageous embodiment a specific angle of the actuating elementor a specific actuating direction can be set by changing the position ofthe resilient element and the actuating element relative to each other.In this case an actuating direction can be set by the user, or bepresettable ex works. To avoid unnecessary material overhead, use ismade of the already available elements (actuating element and resilientelement) in order to achieve an angular adjustment of the actuatingelement in addition. This could be accomplished for example by modifyingor shifting the points of contact of the resilient element on the fixingelement, on the actuating element and/or on an actuator plate that theactuating element has.

Further advantageous embodiments and preferred developments of theinvention can be derived from the description of the figures and/or fromthe dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described and explained in more detail below withreference to the example embodiments depicted in the figures, in which:

FIG. 1 shows a first example embodiment of an actuator having a steelcable pretensioner,

FIG. 2 shows a second example embodiment of a preset actuator,

FIG. 3 shows a third example embodiment of an angularly adjustableactuator in a first position,

FIG. 4 shows a fourth example embodiment of an angularly adjustableactuator in a second position, and

FIG. 5 shows a fifth example embodiment of an angularly adjustableactuator in a third position.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

FIG. 1 shows a first example embodiment of an actuator having a steelcable as a pretensioning element. The actuator has an actuator tip 4 asactuating element and a fixing element embodied as a baseplate 1 asfixing element. The connection arrangement between the said elements isrealized by way of a resilient element which is embodied as acompression spring 2 and a pretensioning element which is embodied as asteel cable 3.

The compression spring 2 and the steel cable 3 constitute simple yetlow-cost components which realize a connection arrangement that effectsa compensating movement in substantially all directions and also allowsa maximum of tolerance compensation. In addition it is possible toabsorb stresses that are produced as a result of impacts or shocks.

Advantageously, the actuator has only one resilient element, i.e. thecompression spring 2, which is the only element that is subject to heavywear and tear. Even if the spring breaks off due to severe stress orheavy wear and tear, the safety function during extraction of theactuator is not compromised. In addition any damage is instantlyrecognizable.

FIG. 2 shows a second example embodiment of a preset actuator. As in thefirst example embodiment the actuator has a baseplate 1, a compressionspring 2, a steel cable 3 and an actuator tip 4, the actuator tip 4being preset in the actuating direction. This presetting is permanent inthis example embodiment, in other words it is preset ex works. The userhas no possibility of tampering with the actuator, as a result of whichmisuse can be ruled out.

Owing to, the presetting of the actuator and also owing to itsflexibility, an unnecessarily great application of force onto the drivehead mechanism of the switch can advantageously be avoided.

Depending on the application of the safety switch it can also beadvantageous to carry out the presetting between the fixing elementembodied as the baseplate 1 and the connection arrangement 2, 3, withthe presetting being permanently preset or modifiable by the user.

An alignment of the actuator tip 4 selectable by the user can berealized for example by way of a screw arresting mechanism.

FIG. 3 shows a third example embodiment of an angularly adjustableactuator in a first position. Compared to the first two exampleembodiments, the actuator of this example embodiment has an actuatorplate 5 disposed between the actuator tip 4 and the connectionarrangement 2, 3, on which actuator plate 5 the actuator tip 4 ismounted non-centrally. The non-central position is not compulsory inthis arrangement. A central position, apposition close to the edge orsimilar positions can also be advantageous depending on the geometryfavored by the particular application. An angular setting of theactuator tip 4 can be set by way of a specific selection of the pointsof contact of the compression spring 2 and/or of the steel cable 3 onthe actuator plate 5, with the steel cable 3 and the compression springin each case assuming a different position relative to each other fordifferent angles.

The steel cable 3 is installed non-centrally inside the compressionspring 2, with the actuator plate 5 together with the actuator tip 4inclining in the direction that is predefined by the shortest distancebetween the steel cable 3 and the compression spring 2.

FIG. 4 shows a fourth example embodiment of an angularly adjustableactuator in a second position. As already stated in relation to thepreceding example embodiments, this example actuator can also be used asan actuator that is preset for a specific actuating direction.

However, this second position which the actuator assumes could alsorepresent a starting position for an actuator whose actuating directionsetting can be set variably, for example by the user, by modifying thepoints of contact described in FIG. 3. In that way the third, fourth andthe following fifth example embodiment would be combined in a kind ofuniversal actuator which can be used in an application-specific mannerfor different actuating devices.

The example embodiments three, four and five could be combined into asingle embodiment if the relative position of the compression spring 2to the steel cable 3 is implemented in a variable manner and theactuating directions of FIGS. 3 to 5 can be realized by a change ofsetting. With this type of universal radius actuator this could beachieved for example on the one hand by way of a steel cable mounted onat least one disk, the position of the cable being modifiable by way ofthe disk. Advantageously, said disk is implemented as rotatable. Inaddition the compression spring 2 can be embodied for the purpose ofchanging the setting in that for example recesses, such as, for example,grooves, in particular annular grooves, provided for receiving thespring are disposed on the baseplate 1 and/or on the actuator plate, therespective groove defining a new point of contact or a differentactuator direction.

FIG. 5 shows a fifth example embodiment of an angularly adjustableactuator in a third position. The statements made in relation to FIG. 3and FIG. 4 can be applied analogously.

To sum up, at least one embodiment of the invention relates to anactuator for actuating a safety switch, the actuator having a fixingelement, an actuating element and a connection arrangement forconnecting the elements. A technical teaching is disclosed whichproposes a universally usable and low-cost actuator. Toward that end,the connection arrangement is realized by way of at least one resilientelement which is pretensioned by way of at least one pretensioningelement. A very simple and robust structure of the connectionarrangement is produced in particular as a result of the internalmounting of the pretensioning element inside the resilient element.

Example embodiments being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the present invention, andall such modifications as would be obvious to one skilled in the art areintended to be included within the scope of the following claims.

1. An actuator for actuating a safety switch, said actuator comprising:a fixing element; an actuating element; and a connection arrangement toconnect the fixing element to the actuating element, the connectionarrangement including at least one resilient element, pretensioned by ofat least one; pretensioning element, to connect the fixing element tothe actuating element.
 2. The actuator as claimed in claim 1, whereinthe resilient element is provided to allow a flexible changing of aposition of the actuating element in relation to the fixing element whenforce is applied.
 3. The actuator as claimed in claim 1, wherein theconnection arrangement is provided to absorb applications of force onthe actuating element at least one of along and perpendicularly withrespect to an actuating direction.
 4. The actuator as claimed in claim1, wherein the pretensioning element is arranged inside the resilientelement.
 5. The actuator as claimed in claim 1, wherein the resilientelement and the pretensioning element are embodied as a single piece. 6.The actuator as claimed in claim 1, wherein the pretensioning element isa steel cable, a wire or a pin.
 7. The actuator as claimed in claim 6,wherein the pin is at least one of movable and resilient.
 8. Theactuator as claimed in claim 1, wherein the resilient element is aspring or a diaphragm.
 9. The actuator as claimed in claim 1, wherein atleast one of the actuating element and the fixing element is alsoprovided for the purpose of pretensioning the resilient element.
 10. Theactuator as claimed in claim 1, wherein the actuator has a mechanism forsetting the actuating direction of the actuating element.
 11. Theactuator as claimed in claim 1, wherein the mechanism for setting theactuating direction of the actuating element has different actuatingdirections in the case of different arrangements of the actuatingelement relative to the resilient element.
 12. The actuator as claimedin claim 1, wherein the mechanism for setting the actuating direction ofthe actuating element is disposed between actuating element andconnection arrangement or between the fixing element and the connectionarrangement.
 13. A safety switch including an actuator as claimed inclaim
 1. 14. The actuator as claimed in claim 2, wherein the connectionarrangement is provided to absorb applications of force on the actuatingelement at least one of along and perpendicularly with respect to anactuating direction.
 15. An actuator for actuating a safety switch, saidactuator comprising: a fixing element; an actuating element; and meansfor connecting the fixing element to the actuating element, the meansfor connecting including at least one resilient element, pretensioned byway of at least one pretensioning element, for connecting the fixingelement to the actuating element.
 16. The actuator as claimed in claim15, wherein the resilient element is provided to allow a flexiblechanging of a position of the actuating element in relation to thefixing element when force is applied.
 17. An actuator for actuating asafety switch, said actuator comprising: a fixing element; an actuatingelement; and means for absorbing applications of force on the actuatingelement at least one of along and perpendicularly with respect to anactuating direction, the means for absorbing including at least oneresilient element, pretensioned by way of at least one pretensioningelement.
 18. The actuator as claimed in claim 17, wherein thepretensioning element is arranged inside the resilient element.
 19. Theactuator as claimed in claim 17, wherein the resilient element and thepretensioning element are embodied as a single piece.
 20. The actuatoras claimed in claim 17, wherein the resilient element connects thefixing element and the actuating element.